Summary of Air Cleaning Technology

All room air cleaners use one or a combination of the following technologies for particles and gases:

For Particles:

Mechanical Filtration (HEPA): High-Efficiency Particulate Air is a pleated filter that holds particles back based on four mechanical principles: Straining, Impingement (Impaction), Interception, Diffusion.
Key Benefits: High initial efficiency at 0.3 microns particle size and below, efficiency increases with usage, no re-release (blowout) of particles, produces no undesirable byproducts, no ozone, no charged particles, and no harmful chemicals.
Key Disadvantages: Filter replacement is required, but IQAir has high-capacity filters which keeps replacement down to a minimum and a filter monitor to let you know when replacement is needed. The filters also install within minutes given the modular design of the IQAir systems.

Electrostatic Precipitation: AKA, "electronic air cleaning", has a first 'ionization stage', where an element with a high voltage gives the particles in the air stream a positive charge. In the second, 'collection' stage, metal plates with a negative high-voltage charge attract the positively charged particles.
Key Benefits: Little air resistance results in relatively high air delivery, no replacement filter cost, up to 80% initial efficiency
Key Disadvantages: Generates lung irritant ozone, requires high maintenance level (weekly cleaning), possible pollutant exposure during cleaning, relatively low efficiency for fine particles, efficiency goes down with usage, captured particles can blow out, charged particles which are not captured are released to the room, loud zapping noise is common.
What the EPA says: "The production of fine particulate material by electronic air cleaners has also been reported" and "...may produce ozone, either as a byproduct of use or intentionally."
(EPA Publication "Residential Air Cleaning Devices: A Summary of Available Information"

Ionization: An element with a high voltage gives the particles in the air stream a negative charge. The charged particles are then attracted to surfaces. Surface can be room surfaces or a deposition surface inside the air cleaner.
Key Benefits: Inexpensive technology (Costs about $2-5 to implement), can be used without a fan because ions spread by themselves (however, they move very little air: between 10 and 20 cfm compared to IQAir HealthPro's 260cfm covering 1100 sq. ft.!)
Key Disadvantages: Releases charged particles which deposit more easily in the lungs, charged particles can soil room surfaces, particles that collect on room surfaces can again become airborne, may produce ozone, high maintenance: weekly cleaning
What the EPA says: "Another factor with respect to ion generators, particularly those that do not trap some of the charged particles, is the effect of particle charging on deposition in the respiratory tract. Experiments have shown a linear increase in particle deposition with charge; therefore, the use of ion generators may not reduce the dose of particles to the lung."
(EPA Publication "Residential Air Cleaning Devices: A Summary of Available Information")
In a nushell: Ionizers cause more inhaled particles to get stuck in our lungs.

Ultraviolet Radiation (UV): An ultra violet tube generates visible and invisible radiation.
Key Benefits: Has the potential to kill some microorganisms
Key Disadvantages: Unreliable and undocumented kill rates due to intensity and contact time, the UV lamps get weaker over time and need to be replaced regularly, exposure to direct UV light is harmful to eyes and skin, UV can break down other components inside the air cleaner.
Other notes: The Centers for Disease Control (CDC) state that UV light in hospitals does not add to the effectiveness of HEPA filtration, UV can decrease filter efficiency if the air cleaner is designed with the UV shining on the filter paper.

Air Washing: Water is mixed with air in order to wash pollutants from the air.
Key Benefits: Requires no filters
Key Disadvantages: Works only with very coarse dust and water soluble gases, the presence of water allows fungi and bacteria to grow, requires regular cleaning and use of problematic fungi and biocides, comparably ineffective technology to remove particles and gases from the air.

Incineration: Convection moves air through a heating coil, same principle as a hair dryer.
Key Benefits: Requires no filters or fans
Key Disadvantages: Moves too little air to make a difference in a normal environment, comparably ineffective technology to remove particles and gases from the air.

Charged Media Filtration: AKA, "fake HEPA", consists of a meshwork of synthetic, electrostatically charged fibers which attract particles.
Key Benefits: Less dense media has less air flow resistance, relatively high initial filter efficiency.
Key Disadvantages: Efficiency decreases with usage.

For Gases:

Quick Note: To be an effective gas filter, it needs to be matched to the gaseous chemical. Most air cleaners offer inadequate gaseous and odor filtration. The following is needed for efficient gas and odor removal: the right media for the pollutant, sufficient contact time, sufficient particle pre-filtration, and sufficient amount of media. Most air cleaners rely on activated carbon alone for gas phase filtration. Activated carbon alone covers only part of the gaseous pollutant range, mainly volatile organic compounds (VOCs). AP1 offers a range of specialty IQAir cleaners which excel in gas phase and odor control thanks to optimized adsorption and chemisorption (explained below).

Ozonation: High-voltage causes the oxygen molecules in the air to combine to ozone (02+0=03).
Misconception: Generates active oxygen - whatever is generated as ozone is taken away in oxygen.
Scientific Fact: At concentration at which ozone is not harmful, it is also not capable of breaking down gas molecules.
What the American Lung Association says: "...because of the documented negative health impact of ozone...American Lung Association suggests that ozone generators not be used." The ALA takes the position that no amount of ozone emitted is acceptable.
What the EPA says: "...ozone is generally ineffective in controlling indoor air pollution." and "Operation of these devices in the presence of VOCs results in a soup of particles and gases."

Photocatalysis: UV light shines onto a catalytic surface, usually titanium oxide, supposed to convert gases into C02 and water (H20).
Misconception: More effective than activated carbon.
Scientific Fact: Activated carbon is better and lasts longer than photocatalysis, and photocatalysis also can produce ozone as a byproduct.
What the EPA says: Activated carbon is more effective.

Adsorption: Physical process of binding gas molecules to a large surface. There are three main adsorption materials used in air cleaners: zeolite, activated carbon, and granulated activated carbon.
Misconception: None.
Scientific Fact: Low activation is best. Highest percentage of micro-pores which are essential for gas phase filtration at low contamination levels found in indoor environments.
Who Uses It? IQAir (IQAir's activated carbon is the most sizable and highest performing in the industry)

Chemisorption: Two stages: First, gas molecules are physically attracted onto a carrier media (activated alumina or impregnated carbon), then secondly, the trapped gas molecules are chemically broken down.
Misconception: None.
Scientific Fact: Since there is a chemical process involved, there is no reemission of gaseous pollutants.
Who Uses It? IQAir

AP1 recommends you stay away from any air cleaning technology which produces charged particles and/or ozone. It is evident, based on our evaluation of the science behind these technologies, that fanless/filterless systems are not only less effective and less efficient, they can be potentially harmful to your health. This is further grounded by the analysis of the US Environmental Protection Agency and the American Lung Association. IQAir systems never produce charged particles or ozone!